UPSTREAM: KVM: arm64: Allow KVM to be disabled from the command line

Although KVM can be compiled out of the kernel, it cannot be disabled
at runtime. Allow this possibility by introducing a new mode that
will prevent KVM from initialising.

This is useful in the (limited) circumstances where you don't want
KVM to be available (what is wrong with you?), or when you want
to install another hypervisor instead (good luck with that).

Reviewed-by: David Brazdil <dbrazdil@google.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andrew Scull <ascull@google.com>
Link: https://lore.kernel.org/r/20211001170553.3062988-1-maz@kernel.org


(cherry picked from commit b6a68b97)
Bug: 204960018
Bug: 271556415
Bug: 275267473
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: Ie796c716fc7cece906a8cded0ae4652a828988bb
(cherry picked from commit a621a4e6)
(cherry picked from commit 57877cc4)